FAIR VALUE DISCLOSURES - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financial assets
Investment securities held-to-maturity	$ 136,744	$ 142,862
Other investments	143,581	125,020
Interest Receivable	27,449
Deposits
Noninterest-bearing	2,723,341	2,643,928
Savings	2,978,250	2,960,979
Time	2,435,858	2,240,441
Carrying value
Financial assets
Cash and short-term investments	332,963	257,639
Investment securities held-to-maturity	136,744	142,862
Other investments	143,581	125,020
Loans held for sale	27,334	13,680
Loans and leases	9,163,934	9,144,015
Interest Receivable	40,386	39,591
Deposits
Deposits	10,635,558	10,210,229
Short-term borrowings	1,397,724	1,316,181
Long-term debt	325,566	414,376
Interest Payable	11,474	13,671
Fair value
Financial assets
Cash and short-term investments	332,963	257,639
Investment securities held-to-maturity	140,065	142,821
Loans held for sale	27,334	13,680
Loans and leases	8,877,637	9,134,215
Interest Receivable	40,386	39,591
Deposits
Deposits	10,644,873	10,209,790
Short-term borrowings	1,397,724	1,316,181
Long-term debt	338,778	414,937
Interest Payable	11,474	13,671
Fair Value, Inputs, Level 1 [Member] | Fair value
Financial assets
Cash and short-term investments	332,963	257,639
Investment securities held-to-maturity	0	0
Loans held for sale	0	0
Loans and leases	0	0
Interest Receivable	0	0
Deposits
Deposits	0	0
Short-term borrowings	1,397,724	1,316,181
Long-term debt	0	0
Interest Payable	2,347	1,899
Fair Value, Inputs, Level 2 [Member] | Fair value
Financial assets
Cash and short-term investments	0	0
Investment securities held-to-maturity	140,065	142,821
Loans held for sale	27,334	13,680
Loans and leases	0	0
Interest Receivable	12,937	12,743
Deposits
Deposits	10,644,873	10,209,790
Short-term borrowings	0	0
Long-term debt	338,778	414,937
Interest Payable	9,127	11,772
Fair Value, Inputs, Level 3 [Member] | Fair value
Financial assets
Cash and short-term investments	0	0
Investment securities held-to-maturity	0	0
Loans held for sale	0	0
Loans and leases	8,877,637	9,134,215
Interest Receivable		26,848
Deposits
Deposits	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Interest Payable	$ 0	$ 0